wachsmuth



Aug. 19, 1958 E. A. WACHSMUTH FREE-PISTON uo'roR-couPaEssoRs OriginalFiled July 8. 1952 5 Sheets-Sheet. 1

$122 Zfiatismzzi Aug. 19, 1958 WAc sMUTH FREE-PISTON uo'roa courasssonsOriginal Filed my 8, 1952 5 Sheets-Sheet 2 Re. 24,522 Reissued Aug. 19,1958 United States Patent 'Ofifice 7 24,522 FREE-PISTON MOTOR-COMPRESSORS Erich A. Wachsmuth, Michigan City, Ind.

Original No. 2,755,988, dated July 24, 1956, Serial No. 297,745, July 8,1952. Application for reissue March 12, 1958, Serial No. 721,068.

Claims priority, application Germany July 11, 1951 25 Claims. (Cl.230-56) Matter enclosed in heavy brackets appears in the original patentbut forms no part of this reissue specification; matter printed initalics indicates the additions made by reissue.

This invention relates to free-piston motor-compressors, and moreparticularly to free-piston motor-compressors of what may be called thecounterstroke type. By this term it is to be understood that two (or amultiple of two) motor-compressor units of the opposed piston type areso arranged and connected that the work strokes of the motor pistons ofone unit are attended by the compression strokes of the motor pistons ofthe other unit, there being mechanical connections between correspondingpiston pairs of .the units and also mechanical connections between themechanically connected pairs so that compression strokes will alwaysattend working strokes, and the constituent elements of the completeorganization shall be properly synchronized. The term mechanically is tobe broadly understood as including all connections, including hydraulic,suited to the maintenance of the needed synchronization.

Among the problems which arise in connection with free-pistonmotor-compressors are those .of starting, regulation to meet varying airdemand, and attendant regulation of power delivered by the motor pistonsof the apparatus, minimization of size in proportion to output, and theavoidance, from the standpoints of simplicity, expense and efiiciency,of all adjuncts which may sound- 1y be dispensed with.

In my application, Serial No. 285,472, filed May 1, 1952, now abandoned,for Starting and Regulating Method for Free-Piston Compressors andApparatus for the Starting and Regulation of Such Compressors, I'havedisclosed, as the title indicates, an arrangement for meeting certain ofthe problems associated with free-piston compressors, and in thispresent application 'a highly desirable solution for the others of theproblems mentioned is disclosed.

Through the use of a counter-stroke free-piston arrangement, in whichthe work necessary .to etfect compression in one set of motor cylinders,in addition to the work of air compression in the compressor cylindersassociated with the other set of motor cylinders, is furnished by thepower generated in the latter cylinders, formerly essential measures forthe pneumatic accumulation of the power needed to effect compressionwithin the motor cylinders are no longer needed, and the large deadspaces of the compressor cylinders characteristic of ordinaryfree-piston machines are eliminated, as well as special buffer spacesfor energy accumulation.

And by virtue of explosive starting, the 'need'for special pneumaticstarting arrangements is removed.

But only if extreme motor simplification and high motor efficiency canbe secured is an optimum aggregate possible. A diesel-type motor, withopposed pistons and with scavenging ports adjacent one end of the commoncylinder for two opposed motor pistons and with exhaust ports adjacentthe otherend will provide a very desirable arrangement, providedadequate scavenging be obtainable without the sacrifice of simplicity ofdesign or freedom from multiplicity of adjuncts. With the elimination ofthe large difierence between the diameter of the motor pistons and thatof the compressor pistons of free-piston motor-compressors as heretoforeconstructed (which provided, as it were, scavenging pump means inherentin the unit), this mode of reflecting scavenging is not available; andthe use .of .a separate scavenging pump systema-nd particularly of amultiple-unit system which a counterstroke free-piston arrangement mightcall for if a separate scavenging pump system were adopted-would becompletely inconsistent with the desired simplicity of the apparatus.

With the machine such .as is shown in application Serial No. 285,472,now abandoned, however, by the use of suitable exhaust and scavengingarrangements, the complete avoidance of any special scavenging devicesis possible, and a further improvement of the mechanical efficiency ofthe machine is attained by the elimination of the scavenging work towhich the machine otherwise :wculd have to be subjected, and anincreased reliability by the elimination of valve trouble.Unidirectional scavenging is a factor in this possibility. Again, thefact is very important that from the first stroke, and practicallyindependent of the load, the machine :operates at a substantiallyconstant rate, so that, notwithstanding the differences in thetemperatures of the :gases in the exhaust lines between starting andworking, a satisfactory operation and starting with self-scavengingwithout additional scavenging aids, and without any need for adjustmentof the exhaust system is obtained.

Briefly, then, there is made possible, with a motorcompressorconstructed and controlled as in said earlier application, through theproper location, sizing and shaping of the exhaust arrangements and ofthe scavenging ports, an entirely automatic self-scavenging without any:auxiliary scavenging air supply, through the utilization of the pressuredrop below atmospheric pressure whichbyv the employment .of an exhaustline which, regarding its volume, is suited to :the working frequency ofthe machinetakes place in the cylinder and in the adjacent portion ofthe exhaust piping until almost to the pointof closing of theexhaust-ports by the piston, which .pres- .sure drop results inaifilling of the cylinder, and even, momentarily, a part of the exhaustpassages, with pure air and a total mass of air in the cylinder. whenthe exhaust .is overrun (covered) by the piston which .traverses itactually in excess of the mass of a volume of air, at atmosphericpressure, equal to the cubic contents of the cylinder at that moment.

It is an object of the invention to provide an improved free-pistonmotor-compressor.and particularly one of maximum simplicity ofconstruction, tree of all auxiliary devices for the provision of extrascavenging air, and wholly automatic in operation from startingthroughout operation under all normal conditions. .Other objects andadvantages 'of the invention will hereinafter appear.

In the accompanying drawings, in which .one illustrative embodimentwhich the invention may assume in .practice certain detail modifications.are shown:

Fig. l is ,a side .elevational view of a free-piston motor-compressorconstructed in accordance with such illustrative embodiment, certainparts being shown in section and certain details of construction notneeded for understanding the invention being omitted.

Fig. 2 is a horizontal, longitudinal section, on the plane of the line22 of Fig. 1, through one pair of motor-compressor piston couples,associated cylinders, etc.

Fig. 3 is a central, longitudinal vertical section through iihemotor-compressor on the plane of the line 3--3 of Fig. 4 is a generallyvertical transverse section on the plane of the line 4-4 of Fig. 3.

Fig. 5 is a considerably enlarged, fragmentary, longitudinal, verticalsection on the plane of the line 5-5 of Fig. 4 through the fuel pumpsand hydraulic impulse givers later described and the controls therefor.

Fig. 6 is an enlarged view, partially in elevation and partially inlongitudinal section, showing details of a motor cylinder liner.

Fig. 7 is a composite sectional view on the planes of the lines 7 7 ---77 and 7 ---7 of Fig. -6, with one quadrant on each section, showingdetails of the scavenging port arrangement.

Fig. 8 is a transverse section on the plane of the line 8-8 of Fig. 6,.through the central zone of the motor cylinder liner.

Fig. 9 is a transverse section on the plane of the line 9-9 of Fig. 2showing the exhaust porting.

Fig. 10 is a detail showing a modified exhaust passage arrangement.

Fig. 11 shows an exhaust passage arrangement with a mufiler.

Fig. 12 is a bottom view of the structure of Fig. 11.

Fig. 13 is a detail of a different exhaust passage arrangement.

Fig. 14 is a fragmentary sectional view on an enlarged scale showingdetails of an impulse giver and associated parts.

Referring now to the drawings, it will be noted that themotor-compressor M comprises, as shown, twin motor cylinders 1, 1 whichhave their axes at least substantially parallel and which are supportedby a frame F. The

cylinder bores are formed in liners L, whose construction will befurther described at a later point in this specification. In the motorcylinders 1, 1 there are reciprocable, in counterstroke relation to eachother, pistons 4, 5 and 4, 5', and these control scavenging ports 2 andexhaust ports 3, both of which port arrangements will be discussed indetail hereinafter.

The four pistons, formed as differential pistons, are coupled in pairs(4 with 4' and 5 with 5'), each pair by a double-armed rocker orcentrally pivoted lever, the pair 4, 4' by the rocker 6 and the pair 5,5 by the rocker 7, so that the outward travels (the working strokes) ofthe pistons 4, 5 associated with the cylinder 1 occur as the inward(compression) strokes of the pistons 4, 5 in the cylinder 1' take place,and vice versa. The two double-armed rockers 6 and 7 are supported forrocking movement respectively by shafts 8 and 9 journaled in the frameF, and they have in fixed relation to them two gear segments 10 and 11which swing in the same directions as their respective rockers; andthese two segments, through their mutual engagement, prevent the pistonsystems from getting out of synchronism with each other. The outer endsof the double-armed rockers are designated 21 and 22 and provided withbearings 24 surrounding pins 25 supported in box or slide elements 26slidably arranged in guideways 27 extending transversely to the severalpistons and providing for guided movement of the elements 26transversely of the pistons as the latter reciprocate.

Compressor cylinders 32 and 33 and 32' and 33' are disposed coaxiallywith the motor cylinders 1, 1, and are open at their ends toward themotor cylinders, but closed at their outer ends by cylinder heads 34,and 34, 35' which carry the suction and discharge valves 36 and 37. Tworeceivers 38 are shown, to which compressor pistons 39, and 39', 40 pumpfluid. Air on its way to the suction valves enters the hollow frame Fthrough filters 41.

The motor cylinders 1 and 1' have fuel pumped to them by pumps P and P'which form parts of a two-cylinder pump unit 0 and these pumps areactuated by the rocker shaft 8, by means of a double-acting cam Cthereon, as will later be explained, and each supplies appropriatelytimed, properly measured shots (injections) of fuel oil to the motorcylinder with which it is correlated through an injection nozzle of anysuitable form and not illustrated in detail because of its conventionalcharacter. The timing of fuel injection and the quantity of fuelinjected is controlled as will be later explained. The fuel conductingconduits from the pumps P and P are respectively designated 43 and 44,and the injection nozzles are indicated at 45 and 46. The fuel oilsupply system to the pumps, being conventional, needs no illustration.

The cylinders 1 and 1 are provided with connections N for receiving theinjection nozzles, and, in addition, one of the cylinders, herein thecylinder 1, is provided at its mid-point, longitudinally, with a chamberstructure P communicating with the mid-point of the motor cylinder bore,and having suitable firing mechanism (not shown) associable with it.

To start the motor-compressor, the pistons 4, 5, are brought in anysuitable manner to their mutually adjacent dead center position, and asmall cartridge, provided with a correctly measured powder charge, isinserted in the chamber structure P", and, when this powder charge isignited, the pistons are forced apart in cylinder 1, and compression iseffected in cylinder 1', so that injection of fuel into cylinder 1 asthe pistons 4', 5 compress the air between them in the cylinder 1 willresult in an explosion occurring in cylinder 1 and a forcing apart ofthe pistons 4 and 5' and a concurrent driving together again of thepistons 4, 5. Each time the pistons uncover the exhaust and scavengingports which they control exhaust and scavenging will be automaticallyeffected as will be later described; and, upon the compression strokesof the motor pistons, the new charges of air will be compressed (andheated) and upon fuel injection, new working strokes will be caused totake place, and, as will be later explained, no auxiliary scavenging airsupply means will be needed, and running will be continued under thecontrol of the apparatus which will now be described in some detail. Theexhaust and scavenging arrangements, their operation, and why they sooperate will be later described and explained.

As previously indicated, the internal combustion engine cylinders 1 and1, which are illustrated as forming portions of opposed piston, dieselengine units, are adapted to have fuel oil pumped to them respectivelyby the pumps P and P of a two-cylinder fuel pump 0. The construction ofthese pumps may be of any suitable conventional form, having provisionfor automatic variation of the instant of fuel delivery and the durationof such delivery, the variation being effected in a generally well-knownmanner, as by the reciprocation of a rack bar R, Which rotates the pumpplungers on their axes in such a manner as to vary the fuel delivery ofthe pump between a maximum and zero. By the proper shaping of the usualslanting control edge of the pump plunger, practically any rate of fueldelivery can be effected as a function of the angle of rotation of thepump plungers. In view of the full discussion in Serial No. 285,472 nowabandoned, there need be no extended discussion of this here, and it maysimply be said, for purposes of illustration, that the rack bar R isdisplaced as a function of receiver pressure under the control of areceiver pressure responsive cylinder and piston mechanism K and thatthe control edge of the pump plunger will be so formed and the movementsof the rack bar R be coordinated with receiver pressure in such a mannerthat when receiver pressure is at atmospheric pressure there is suppliedthe proper quantity of fuel to be burned to effect starting; whenreceiver pressure is at 14.7 pounds gauge there is supplied the properquantity of fuel to be burned to effect the compression and dischargeagainst that pressure of the quantity of air taken in; and as receiverpressure increases the quantity of fuel injected is properly in- 5creased. Of course, the quantity of fuel injected at each receiverpressure provides .for the work of compression of the scavenging airsupplied to the motor, as well as for the compression and discharge ofair taken into the compressor cylinders.

Another receiver pressure responsive device K controls the quantity ofair delivered, and this pressure responsive device, which becomesoperative as a control as soon as receiver pressure exceeds the normallower limit of the designed operating range, for example, sevenatmospheres gauge, does so through hydraulic impulse givers I, I whichmay be of essentially the same type of construction as the pumps P, P.Within the normal operating range, say from 7 atmospheres gauge to 7.7atmospheres gauge, the device K ano'ther cylinder and piston mechanismas shownadjusts the amount of air delivered by the compressor all theway from maximum down to zero delivery, if receiver pressure continuesto rise, as might occur if all air use were discontinued. The impulsegivers I, I as illustrated are arranged side by side, one above theother, and are adapted to be caused to give their impulses inalternation by suitable cam actuating means C. The pumps P', P and theimpulse givers I, I are respectively actuated by cams C and C, each, asshown, a double cam, mounted respectively on'the shafts 8 and 9. As inthe case of the fuel pump, the control element of each impulse giver isa plunger with a sloping control edge reciprocated in rhythm with themotor-compressor piston with which it is coordinated and moving in abore in a cylinder which is provided for it. The shape of the controledge is determined empirically, in connection with the mechanicalcoupling for the control rod of the fuel pump, so that for each loadstage of the compressor the work output of the motor and the workabsorbed by the compressor are in equilibrium.

During each reciprocation of its pistons the impulse givers I and -I'produce hydraulic impulses which are used to control fingers cooperatingwith the compressor suction (inlet) valves in such a way that thesuction valves are held open for a smaller or larger portion of thecompression strokes of the compressor pistons 39, 40 and 39', '40. Eachof the impulse givers acts simultaneously on two finger systems, oneassociated with each of the alined compressor cylinders of a pair. Inapplication Serial No. 285,472 two ditferent possible means for ef--fecting different degrees of unloading are illustrated. In this presentapplication but one will be described for purposes of illustration, andit will correspond generally to the second means disclosed in theearlier filed case mentioned.

The impulse givers I and I each comprise, as shown in Fig. 5, a cylinder50 connected with a supply space 51 to which a hydraulic fluid isconducted from any suitable reservoir (not shown), by a port 52, andcontaining a plunger 53 having a control edge 54 generally helicallyextending about its periphery at its working end. The plungers areactuated in turn by the cam C and are adapted to be rotated by a rackbar R under the control of the pressure responsive device K to changethe timing of the fluid impulses. The cylinder 50 of the impulse giver Iis connected by conduits with cylinder and piston mechanisms which openthe inlet valve associated with the cylinders 32 and 33, and the impulsegiver I is similarly connected by conduits with cylinder and pistonmechanisms which open the inlet valves of the cylinders 32' and 33'.These conduits are numbered 58 and 59 in the case of impulse giver I and58' and 59 in the case of impulse giver I. These last cylinder andpiston mechanisms, numbered 60 actuate finger mechanisms 61 which arearranged to unseat and hold open inlet valves and to have their valveopening movements limited by stops 62. To provide for necessarymaintenance of the inlet valves open during a portion of the dischargeStrokes of the compressor pistons, an accumulator A is associated witheach conduit 58, and comprises a chamber forming member 63 in whichaspring 64 acts to press a septumforming member 65 in a direction tominimize the volume of fluid in the chamber which communicates with theconduit 58. It will be understood that the accumulators A, may usediaphragms, bellows, or any other desired equivalents of pistons tominimize or prevent fluid leakage.

The outward (pumping) movements of the pistons or plungers 53, are, inthe arrangement shown, coordinated with the suction strokes of thecompressor pistons. In other words, the movements of the plungers intheir cylinders occur during the suction strokes of the compressorpistons. The oblique control edges 54 determine the beginning of fluiddelivery. The outwardly moving plungers at first force fluid from theircylinders back into the supply space and then, when the control port is,coveredearlier or later depending on the amount of plunger rotationbythe slanting control edge on the plunger, fluid delivery to the conduits58 or 58 commences and the finger operating cylinder and pistonmechanisms have their pistons move into position to hold the inletvalves in open position. After the finger operating pistons reach thelimits of their movement, as determined by appropriate abutments orstops 62, the fluid delivered by further plunger movement is stored inthe accumulator. Delivery and storage in the accumulator of fluidcontinues until the cam reaches its limit of swing, and upon reversemovement of the cam the system still remains under the pressureresulting from the presence of the accumulator until the latter isempty. Only then do the inlet valves close. The inlet valves close atthe moment the slanting control edge uncovers the bypass port. Theplungers continue inward movement in their cylinders, and the spacebeing enlarged byinward movement of the plunger is filled from thesupply space until the dead position is reached.

Further details with respect to this mechanism may be had by referenceto the copending application hereinabove mentioned.

As previously noted, the adjustment of the fuel supply to the work ofcompression and discharge of the air (which is dependent on the receiverpressure), and of the quantity of air to be handled, are obtained bygiving a suitable form to the fuel-pump control-edges and to thecontrol-edges of the impulse givers controlling the quantity of airdelivered, and rotating the plungers of these devices on their axes.

Pressure responsive device K as above pointed out, is a device actingbetween p. s. i. gauge and the lower limit of the designed pressurerange, and it consists of a cylinder 66, a piston 67 having a piston rod68, and a spring 69. 70 represents the point of pivotal connection ofthe piston rod 68 with a two-armed lever 71, which is connected, on theone hand, at 72, with the regulating rack R of the fuel pumps P and P,and, on the other hand, at the articulation point 73, with theregulating rack bar R of the impulse givers I and I which control thequantity of air pumped by the compressor. The pressure responsive deviceK acting over the pressure range between the lower and the upperdesigned operating pressures consists of a cylinder 74, a piston 75having a piston rod 76, and a spring 77 suitably tensioned to cause itto commence to yield only when the lower rated pressure (as aboveexplained, for illustration, 7 atmospheres) is exceeded. (It may be maderesponsive to the excess of receiver pressure over a predeterminedpressure, by the use of a suitable relief valve permitting only theexcess to pass it.) Due to the high spring tension and the relativelysmall effective pressure, the active range of this device is but small.-It transmits, via a lever 78, pivoted at 79'and acting on the controlelement R at the other end of the latter, adjustments to theregulating-rod .R' necessary for the regulation to be accomplishedbetween zeroand fullload. 80 and 81 are pressure lines connecting thedevices K and K respectively with the receiver.

It will be understood that with twin pumps and twin hydraulic impulsegivers the elements R and R might be duplicated, each pump and eachimpulse giver having a control rack individual to it and those of eachpair being then concurrently actuated. This duplication, however, isunnecessary.

The symmetrical arrangement of the fuel pumps and impulse givers makesit requisite that the cams which actuate them be arranged with theirangled control surfaces facing towards each other.

The positions of the parts in Figs. 1, 2, 3, and 5 correspond to theconditions present before starting of the compressor. With risingreceiver pressure, the piston 67 moves, against the pressure of thespring 69, upwardly in Fig. 5, while the piston 75, owing to theconsiderably higher initial tension of the spring 7'7, remains at firstat rest. The piston 67, moving upwardly, displaces, through the lever71, swinging about the then stationary point 73, the regulating rod R,in accordance with the increasing work of compression, toward full loadposition, which is reached at the upper position of the piston 67',corresponding to the lower limit of the de signed normal pressure range.If the receiver pressure continues to rise further, the piston '75commences to move downwardly, and to displace, through the rack bar R,which thereupon moves upward, that is, in the direction of zero airdelivery, and through the lever 71, which is now swinging about the nowstationary point 70, the regulating rod R of the fuel pump downward,that is, toward no-load running position.

The motor-compressor described will operate, beginning with the veryfirst stroke, at substantially its normal (designed) rate (strokes perminute), and will maintain substantial uniformity of rate regardless ofload variations.

The several views disclosing the motor cylinder liner L may now beadvantageously noted. It will be seen that this liner is formed withsuitable circumferential ribs which serve to center it and, throughtheir close fit with the surrounding wall of the frame F, provide sealsfor cooling water passages. It will be noted that centrally, lengthwise,the sleeve or liner L has an annular enlargement 91 which is traversedperipherally by obliquely longitudinally extending (helically arranged)grooves 92 for cooling water passage and which is traversed radially bythreaded openings 93 for the reception of a fuel injection nozzle, and94, for the chamber-forming device P in which the powder charge is to beplaced for starting. At opposite sides of its longitudinal center theliner is provided with exhaust openings and with scavenging,airadmitting, openings. The exhaust openings or slots, 96, are four innumber, as shown, and these are tangentially directed, and each hasassociated with it an at least initially independent exhaust pipe97-this for the conduction of the exhaust gases in as undisturbed andfrictionfree as possible a manner. Desirably, as shown in Fig. l, theexhaust pipes may be conical, increasing in cross section as theirextension from the exhaust ports increases. Cylindrical pipes, as shownin Fig. 13, are not excluded, but are considered less advantageous. Ajunction of two neighboring pipes is possible as shown in Fig. 10, andwhen this is employed the junction may well be made at a distance fromthe exhaust slots which corresponds to half the travel of the pressurewave front, later discussed, during the pre-exhaust periods.

The pipe length for best self-scavenging may be calculated approximatelyfrom the speed of the machine in cycles per minute, the instants anddurations of opening of exhaust and scavenging ports, and theempirically deter mined rate of wave travel in the exhaust passages. Inthe illustrated machine, with about 1200 cycles per cylinder per minute,a pipe length of about 2.20 meters is arrived at by calculation. Inmaking such'calculations, one starts with the assumption that,substantially concurrent with the closing of the inlet or scavengingslots by the scavenging slot-overrunning piston, a compression wavearises at the still open exhaust slots which prevents, in spite of themovements of the motor pistons towards each other, any further pushingout of air during the period the exhaust ports remain open after closureof the scavenging slots, and makes possible in effect a degree ofsupercharging of the motor. The final determination of the optimum pipelength is empirical.

The scavenging port arrangement may now be noted. It will be observed,by inspection of Fig. 6, that there is formed a relatively widecircumferential groove 100, surrounding the liner L, and that, as shown,four rows of scavenging slots 101 101 101 and 101 traverse the wall ofthe liner and open into the groove 100. These rows, as may be seen fromFig. 7, are made up of port openings sloping slightly towards theexhaust openings and which, in the row most remote from the centerpoint, longitudinally, of the sleeve or liner L have their axes inradial planes, and, in succeeding rows, have their axes in planes whichare tangent to larger and larger cylinders, so that at the row firstuncovered by the motor piston relatively great whirling action is giventhe entering air, and this whirling action is diminished in succeedingrows and is absent in the row which is last uncovered.

The row which is uncovered first and closes last is not uncovered untilafter a substantial opening of the exhaust ports has taken place, andthe covering of this row takes place substantially before the exhaustports are recovered by the piston which moves over them. The timeinterval between the initiation of opening of the exhaust ports 3 andthe initiation of openingof the scavenging ports 2 is called thepre-exhaust period, and its duration is of considerable importance. Itshould be sufficient so that, at the full normal rated C. P. M. (cyclesper minute) of each motor, there shall have been such a completedischarge of the combustion products that there shall be justcommencing, in the portion of the cylinder through which the firstuncovered scavening ports 2 open, to be a reduction of cylinder pressurebelow atmospheric, so that atmospheric air will rush through thescavenging slots not only due to the suction effect produced by thestill mutually separating motor pistons but also due to thesuction-pressure effect caused by the correspondingly dimensionedexhaust pipes. Due to this effect there will be produced, during theremainder of the separation strokes of the pistons, a condition in themotor cylinder which will result in a filling not only of the maximumvolume thereof with clean scavenging air, but an actual flow into theportions of the exhaust pipes nearest the cylinder exhaust ports, ofsome of the scavenging air. Then, as the pistons reverse and move towardeach other, there will be a pressure wave in the exhaust pipes whichwill, after the scavenging ports have again been covered, and despitethe fact that the pistons are then approaching each other and that theexhaust ports are still partially open, not only prevent escape to theexhaust pipes of fresh scavenging air from the cylinder, but indeed Willaid in a substantial supercharging effect, since there will be in thecylinder, in which a pressure increase is being effected by inwardpiston movement, a further pressure increase due to the additional airquantity forced in from the exhaust pipes. The exhaust ports will beclosed off from communication with the cylinder bore before any productsof combustion could attain to the cylinder from the exhaust pipes. Thereturn movement of gases through the exhaust pipes will force the airthat has entered those pipes back through the exhaust ports.

With this arrangement it will be noted that a substantial increase inpower is provided, and a very efficient operation assured. Because ofthe particular nature and operating characteristics of the free-pistonmotor-compressor unit described it is possible to avoid the need for any9 auxiliary scavenging devices, or superchargers, and to start, and tomaintain efiicient operation throughout the entire range of loadvariations encountered in use. 7

It is possible to employ mufflers with apparatus of the characterdescribed; and Figs. 11 and 12 show an arrangement on which the balancedexhaust pipes, instead of opening directly to atmosphere, go to a commonmufiier, Fig. 11 showing aside view and Fig. 12 a bottom view of thisarrangement.

Apparatus of the character hereinabove disclosed for purposes ofillustrationis capable of operating, with freedom from the disadvantagesof conventional free-piston compressors, with minimum sizeper unit ofair delivered, and without any auxiliary scavenging means whatever i. e.wholly by self-scavenging (I) because of its explosion starting,permitting .nice proportioning of the power to the work to be done onthe first stroke, and immediate initiation of the working of the exahustgases in the exhaust line effecting self-scavenging; '(2) because fromthe very first stroke on it can operate essentially at its designednumber of cycles per unit of time, any such frequency variations as mayoccur initially notbeing sufiicient to prevent satisfactoryself-scavenging; 3) because the twin construction and counter-strokerelation between corresponding motor-compressor piston couples insurescompression in one motor cylinder while the ignited fuel forces thepistons in the other motor cylinder apart; (4) because the apparatusenables the omission of so'many not only new -unnecessary, -but.poorefiiciency engendering complications; 5) because of the effectivematching at all times of power to Work to be performed; and not tomention more in this summary, (6) because the self-scavenginginsuresanincrease of power generated, as well as an avoidance of power lossesthrough unneeded auxiliary scavenging .pumps. Whether or not all of theenumerated factors are essential, they contribute to the improvedresults.

While there are in this application specifically described one form andcertain modifications which the invention may assume in practice, itwill be understood that this form and certain modifications of the sameare shown forpurposes of illustration, and that the in-.

vention may further be modified and embodied in various other formswithout departing from its spirit'o'r the scope of the appended claims.

What I claim is: v

1. In combination, in a motor driven compressor, a diesel motor havingfuel-pumping meanshaving' an adjustment for the quantity of 'fuel pumpedand a compressor actuated by said motor and having a device for varyingthe quantity of fluid delivered per stroke, which device has anadjustment which controls the quantity ofdelivered fluid, a pressureresponsive deviceresponsive to compressor discharge pressure fromatmospheric pressure to the lower limit of the designed operating range,another pressure responsive device responsive to compressor dischargepressure from said lower "limit to the maximum desired compressordischarge pressure, an operating connection between said first mentionedpressure responsive device and said first mentioned adjust ment by whichsaid device causes said adjustment to increase fuel supply withincreasing compressor discharge pressure, said operating connectionincluding a lever to which, between its ends, said first mentionedpressure responsive device is connected and which has one of itsoppositearms connectedto s'aidfirst mentioned adjustment, an operatingconnection between said second mentioned pressure responsive device andsaid second mentioned adjustment by which said second mentioned pressureresponsive device causes said second mentioned adjustment to reduce thequantity of fluid compressed and delivered per stroke as compressordischarge pressure increases from said lower limit, and a furtherconnection actuated 'by said second mentioned pressure responsive deviceand connected with-the arm of said first mentioned lever which is notconnected with said first mentioned adjustment for causing said firstmentioned adjustment .to reduce fuel delivery proportionally toreduction in fluid delivered, said diesel motor having a cylindercontaining opposed pistons and exhaust ports uncovered by one .of saidpistons and scavenging ports uncovered by the other of said pistons atan instant at which motor cylinder pressure starts to fall belowatmospheric, said exhaust ports having connecting with'them an exhaustsystem in which successively there are produced a pressure wave, asubatmospheric pressure and a return pressure wave, the last twoeffecting the induction through the scavenging ports and the supply forcompression within said motor cylinder of all the scavenging airrequired by said motor under any normal operating conditions.

2. In combination, in a motor driven compressor which comprises a dieselmotor having fuel-pumping means having a plunger with a slanting controledge and having an adjustment for rotating said plunger to vary thequantity of fuelpumped, and a compressor having a control for varyingthe quantity of fluid delivered per stroke, which control has anadjustment which controls the quantity of delivered fluid, a pressureresponsive device responsive to compressor discharge pressure fromatmospheric pressure to the lower limit of the designed operating range,another pressure responsive device responsive to compressordischargepressure from said lower limit to maximum desired compressor dischargepressure, an operating connection between said first mentioned deviceand said .first mentioned adjustment by which said device causes saidadjustment to increase fuel supply with increasing compressor dischargepressure, said operating connections including mechanical connectionstransmitting adjusting move- -ments, directly proportional to themovement of said first pressure responsive device, to said plunger, anoperating connectionbetween said second mentioned device and said secondadjustment by which said second mentioned device causes said secondmentioned adjustment to reduce the quantity of fluid compressed anddelivered per stroke as compressor discharge pressure increases fromsaid lowerlimit, and a further connection actuated by said secondmentioned device for causing said first mentioned adjustment to reducefuel delivery proportionally to reduction in fluid delivered, saiddiesel motor having a cy'lindercontaining opposed pistons and exhaustports uncovered by one of said pistons and scavenging ports uncoveredbythe other of said pistons at an instant at which motor cylinderpressure starts to fall below atmospheric, said exhaust ports havingconnecting with them an exhaust system in which successively there areproduced a'pressure wave, a sub-atmospheric pressure and a returnpressure wave, the last two effecting the induction through thescavenging ports and the supply for compression within said motorcylinder of all the scavenging air required by said motor under anynormal operating conditions.

3. In combination, in a motor driven compressor, a diesel motor havingfuel-pumping means having an adjustment for the quantity of fuel rpumpedand a compressor actuated .by said .motor and having a device forvarying the quantity of fluid delivered per stroke, which device has anadjustment which controls the quantity of delivered fluid, a pressureresponsive device responsive to compressor discharge pressure fromatmospheric pressure to the lower limit of the designed operating range,another pressure responsive device responsive to compressor dischargepressure from said lower limit to the maximum desired compressordischarge pressure, an operating connection between said first mentionedpressure responsive device and said first mentioned adjustment by whichsaid device causes said adjustment to increase fuel supply withincreasing compressor discharge pressure, an operating connectionbetween said second 11 mentioned pressure responsive device and saidsecond mentioned adjustment by which said second mentioned pressureresponsive device causes said second mentioned adjustment to reduce thequantity of fluid compressed and delivered per stroke as compressordischarge pressure increases from said lower limit, and a furtherconnection actuated by said second mentioned pressure responsive devicefor causing said first mentioned adjustment to reduce fuel deliveryproportionally to reduction in fluid delivered, said diesel motor havinga cylinder containing opposed pistons and exhaust ports uncovered by oneof said pistons and scavenging ports uncovered by the other of saidpistons at an instant at which motor cylinder pressure starts to fallbelow atmospheric, said exhaust ports having connecting with them anexhaust system in which successively there are produced a pressure wave,a sub-atmospheric pressure and a return pressure wave, the last twoeffecting the induction through the scavenging ports and the suppy forcompression within said motor cylinder of all the scavenging airrequired by said motor under any normal operating conditions.

4. In combination, in a motor driven compressor which comprises a dieselmotor having a fuel-pumping means having a plunger and an adjustment forrotating said plunger to vary the quantity of fuel pumped, and acompressor having a control for varying the quantity of fluid deliveredper stroke, which control has an adjustment which controls the quantityof delivered fluid, a pressure responsive device responsive'tocompressor discharge pressure from atmospheric pressure to the lowerlimit of the designed operating range, another pressure responsivedevice responsive to compressor discharge pressure from said lower limitto maximum desired cornpressor discharge pressure, an operatingconnection between said first mentioned device and-said first mentionedadjustment by which said device causes said adjustment to increase fuelsupply with increasing compressor discharge pressure, said operatingconnections including mechanical connections transmitting adjustingmovements, directly proportional to the movement of said first pressureresponsive device, to said plunger, an,operating connection between saidsecond mentioned device and said second adjustment by which said secondmentioned device causes said second mentioned adjustment to reduce thequantity of fluid compressed and delivered per stroke as compressordischarge pressure increases from said lower limit, and means actuatedby said second mentioned device for causing said first mentionedadjustment to reduce fuel delivery proportionally to reduction in fluiddelivered, said diesel motor having a cylinder containing opposedpistons and exhaust ports uncovered by one of said pistons andscavenging ports uncovered by the other of said pistons at an instant atwhich motor cylinder pressure starts to fall below atmospheric, saidexhaust ports having connecting with them an exhaust system in whichsuccessively there are produced a pressure wave, a sub-atmosphericpressure and a return pressure wave, the last two eflFecting theinduction through the scavenging ports and the supply for compressionwithin said motor cylinder of all the scavenging air required by saidmotor under any normal operating conditions.

5. In an apparatus for regulating the operation of an internalcombustion engine operated free-piston comprcssor having a normalworking range having lower and upper limits, said internal combustionengine operated free-piston compressor having also a discharge pressurerange traversed during its building up of its discharge pressure to thelower limit of such normal range, the period of operation of saidinternal combustion engine operated free-piston compressor during thebuilding up of its discharge pressure to the lower limit of its normalworking pressure range being hereinafter referred to as period (1) andthe period of operation between such upper 'and lower limits'beinghereinafter referred to as period (2), in combination, two expansiblechamber devices, each subjected to and governed by compressor dischargeline pressure, one eflectivegto exercise control during period (I)aforesaid and the other during period (2) aforesaid, a fuel pump havinga regulating element, a lever movable to control said regulating elementin such a manner that actuation of said lever in a given directionefiects increasing fuel quantity delivery, said one expansible chamberdevice operatively connected with said lever to move the latter in adirection to increase fuel quantity with increasing compressor dischargepressure and said one pressure responsive device having a limited motionat the extreme of which it arrives when the pressure in the compressordischarge line reaches the lower limit of the normal working pressurerange, and said other expansible chamber device being set to commence tooperate when the compressor discharge pressure reaches said lower limitand constructed to attain to a limit of operation when the compressordischarge pressure reaches the upper limit of the normal workingpressure range, said second expansible chamber device acting on saidlever to move the same, upon increasing discharge line pressure, in adirection to decrease fuel quantity and when it reaches its limit ofoperation reducing fuel quantity to that requisite for no-loadoperation, and a device controlling the volume of air compressed andconnected with said lever and 'movable to reduce the volume of aircompressed, as the injected fuel quantity is reduced, from a maximum tozero.

6. 'In combination, in a motor driven compressor whichcomprisesfuel-pumping means having an adjustment for the quantityof'fuel pumped, a device for varying the quantity of fluid delivered perstroke which device has an adjustment which controls the quantity ofdelivered fluid, a pressure responsive device responsive to compressordischarge pressure from a base pressure to the lower limit of thedesigned operating range, another pressure responsive device responsiveto compressor discharge pressure from said lower limit to maximumdesired com pressor discharge pressure, an operating connection betweensaid first mentioned pressure responsive device and said first mentionedadjustment by which said pressure responsive device causes saidadjustment to increase fuel supply with increasing compressor dischargepressure, an operating connection between said second mentioned pressureresponsive device and said second adjustment by which said secondmentioned pressure responsive device causes said second mentionedadjustment to reduce the quantity of fluid compressed and delivered perstroke as compressor discharge pressure increases from said lower limit,and a further connection actuatea'tby said second mentioned pressureresponsive device for causing said first mentioned adjustment to reducefuel deliveryprogressively as reduction in fluid delivered occurs.

7. In combination, in a motor driven compressor which comprisesfuel-pumping means having an adjustment for the quantity of fuel pumpedand which further comprises a device for varying the quantity of fluiddelivered per stroke which device has an adjustment which controls thequantity of delivered fluid, a pressure responsive device responsive tocompressor discharge pressure from atmospheric pressure to the lowerlimit of-the designed operating range, another pressure responsivedevice responsive to compressor discharge pressure from said lowerlimitto maximum desired compressor discharge pressure, on operatingconnection between said first mentioned pressure responsive device andsaid first mentioned adjustment by which said pressure responsive devicecauses said adjustment to increase fuel supply with increasingcompressor discharge pressure, said operating connection including alever to which, between its ends, said first mentioned pressureresponsive device is connected andwhich has one of its opposite armsconnected to-said first mentioned adjustment, an operating connec- 13tion betweensaid .second mentioned pressure responsive device and saidsecond mentioned adjustment by which said second mentioned pressureresponsive device causes said second mentioned adjustment to reduce thequantity of fluid compressed and delivered 'per stroke as compressordischarge pressure increases from said lower limit, and a furtherconnection actuated by said second mentioned pressure responsive deviceand connected with the arm of said first mentioned lever which is notconnected with said first mentioned adjustment for causing said firstmentioned adjustment to reduce fuel delivery progressively as reductionin fluiddelivered takes place.

8. In combination, in a motor driven compressor which comprisesfuel-pumping means having a plunger with a shaped control-edge and anadjustment for the quantity of fuel pumpedand which motor drivencompressor further comprises a device forvarying the quantity of fluiddelivered per stroke, which device has an adjustment which controls thequantity of delivered fluid, a pressure responsive device responsive tocompressor discharge pressure from a lower pressure to the lower limitof the designed operating range, another pressure responsive deviceresponsive to compressor discharge pressure from said lower limit tomaximum desired compressor discharge pressure, an operating connectionbetween said first mentioned pressure responsive device and said firstmentioned adjustment by which said pressure responsive device causessaid adjustment to increase fuel supply with increasing compressordischarge pressure, said operating connection including a movementvarying device actuated by said first mentioned pressure responsivedevice for maintaining fuel delivery in step with compressor dischargepressure changes, an operating connection between said second mentionedpressure responsive device and said second adjustment by which saidsecond mentioned pressure responsive device causes said second mentionedadjustment to reduce the quantity of fluid compressed and delivered perstroke ascompressor discharge pressure increases from said lower limit,and a further connection actuated by said second mentioned pressureresponsive device for causing said first mentioned adjustment to reducefuel delivery in step with reduction in fluid delivered.

9. In combination, in a motor driven compressor which comprisesfuel-pumping means having a plunger with a control-edge modified from atrue helix and having an adjustment for the quantity of fuel pumped, adevice for varying the quantity of fluid delivered per stroke whichdevice has an adjustment which controls the quantity of delivered fluid,a' pressure responsive device responsive to compressor dischargepressure from a lower base pressure to the lower limit of the designedoperating range, another pressure responsive de-vice responsive tocompressor discharge pressure fromsaid lower limit to maximum desiredcompressor discharge pressure, an operating connection between saidfirst mentioned pressure responsive device and said first mentionedadjustment by which said pressure responsive device causes saidadjustment to increase fuel supply with increasing compressor dischargepressure, said operating connections including mechanical connectionstransmitting adjusting movements, directly proportional to the movementof said first pressure responsive device, to said plunger, an operatingconnection between said second mentioned pressure responsive device andsaid second adjustment by which said second mentioned pressureresponsive device causes said second mentioned adjustment to reduce thequantity of fluid compressed and delivered per stroke as compressordischarge pressure increases from said lower limit, and a furtherconnection actuated by said second mentioned pressure responsive devicefor causing said first mentioned adjustment to reduce fuel delivery instep with the reduction in fluid delivered.

10. In an apparatus for varying the quantity of fluid delivered perstroke by a compressor which includes a 14 reciprocable piston,a-.cylinder for said piston, 'saidcylinder and piston coacting to formachamberin which com pression of a fluid 'is-efiected 'by relativemovement betweensaid cylinder and piston, said cylinder-having an inletvalve, a shaft and a connection, between said .shaft andpistonisuch-that,th-ey move together, in combination,

hydraulically operable 'expansible chamber mechanism for holding theinlet valve open through a portion ofthe discharge stroke of the piston,a hydraulic impulse giver having'meansifor varying the period-over whichit delivers its impulse, meansconnecting said impulse giver with saidhydraulically operable expansible chamber mechanism whereby impulsesdelivered by the former control the-operation of the latter, and meansgoverned by, compressor discharge pressure for adjusting said means forvarying the period of delivery ofthe impulse by saidimpulse giver tovary suchperiod.

11. In an apparatus for varying'the quantity of fluid delivered perstroke by a compressor which includes areciprocable piston, a cylinderfor said piston, said'cylinder and piston coacting to, form a chamber inwhich compression of a fluid is effected by relative movement betweensaid cylinder and piston, said cylinder having an inlet valve, a shaftand a connection between said shaft and piston such that they movetogether, in combination, hydraulically operable expansible chambermechanism for holding the inlet :valve open through a portion of thecompression stroke of the piston, a hydraulic impulse giver having meansfor varying the duration of its impulses, conduit means connecting saidimpulse giverwith said hydraulically operable expansi'ble chambermechanism and transmitting impulses delivered by the former to thelatter, and means responsive to compressor discharge pressure foradjusting said means for varying the duration of the delivery of theimpulses by said impulse giver to vary 'such duration.

12. In apparatus for varying thequantity of "fluiddelivered per strokeby a compressor which includes a reciprocable piston, a cylinder forsaid piston, said cylinder and piston coacting to form a chamber inwhich cornpression of a fluid is effected by relative movement be tweensaid cylinder and piston, said cylinder having an inlet valve, a shaftand a connection between said shaft and piston such that they movetogether, in combination, hydraulically operable expansible chambermechanism for holding the "inlet valve open through a portion of thecompression stroke of the piston, a hydraulic impulse giver having meansfor varying its delivery of its impulse, conduit means connecting saidimpulse giver with said hydraulically operable expansible chambermechanism whereby impulses delivered by the former control the operationof the latter, means controlled by said shaft for causing said impulsegiver to initiate an impulse during the'suction stroke of said piston,and means governed by compressor discharge pressure for adjusting saidmeans for varying the delivery of the im* pulse by said impulse giver tovary the time during which the expansible chamber mechanism is subjectto the impulse.

13. In an apparatus for varying the quantity of fluid delivered perstroke by a compressor which includes a reciprocab'le piston, a cylinderfor said piston, said cylinder and piston coact ing to form a chamber inwhich compression of a fluid is effected by relative movement betweensaid cylinder and piston, said cylinder having an inlet valve, a-shaftand a connection between said shaft and piston such that they move ingiven relation to each other, in combination, hydraulically operableexpansible chamber mechanism for holding the inlet valve open through aportion of the compression stroke 'of the piston, a hydraulic impulse.giver having an angularly displaceable plunger having a shaped controledge for varying the period of delivery of its impulse, conduit meansconnecting said impulse giver with said hydraulically operableexpansible chamber mechanism whereby impulses delivered by the formercontrol the operation of the latter, means controlled by said shaft forcausing said impulse giver to initiate its impulse during the suctionstroke of said piston, and 'means governed by compressor dischargepressure for adjusting said angularly displaceable plunger for varyingthe time during which the expansible chamber mechanism is subject to theimpulse.

14. In an apparatus for varying the quantity of fluid delivered perstroke by a compressor which includes a reciprocable piston, a cylinderfor said piston, said cylinder and piston coacting to form a chamber inwhich compression of a fluid is effected by relative movement betweensaid cylinder and piston, said cylinder having an inlet valve, anoscillating shaft and a connection between said shaft and piston suchthat they move in given relation to each other, in combination,hydraulically operable expansible chamber mechanism for holding theinlet valve open through a portion of the compression stroke of thepiston, a hydraulic impulse giver having means for varying the periodduring which it delivers its impulse, conduit means connecting saidimpulse giver with said hydraulically operable expansible chambermechanism whereby impulses delivered by the former control the operationof the latter, and means governed by compressor discharge pressure foradjusting said means for varying the period of delivery of the impulseby said impulse giver to vary its duration.

15. In an apparatus for varying the quantity of fluid delivered perstroke by a compressor which includes a reciprocable piston, a cylinderfor said piston, said cylinder and piston coacting to form a chamber inwhich compression of a fluid is effected by relative movement betweensaid cylinder and piston, said cylinder having an inlet valve, a shaftand a connection between said shaft and piston such that they move in agiven relation to each other, in combination, hydraulically operableexpansible chamber mechanism for holding the inlet valve open through aportion of the compression stroke of the piston, a hydraulic impulsegiver, conduit means connecting said impulse giver with saidhydraulically operable expansible. chamber mechanism whereby impulsesde-' livered by the former control the operation of the latter, andmeans governed by compressor discharge pressure for varying the controlby said impulse giver of said hydraulically operable expansible chambermechanism.

16. In an apparatus for varying the quantity of fluid delivered perstroke by a compressor which includes a reciprocable piston, a cylinderfor said piston, said 'cylinder and piston coacting to form a chamber inwhich compression of a fluid is eflected by relative movement betweensaid cylinder and piston, said cylinder having an inlet valve, a shaftand a connection between said shaft and piston such that they move ingiven relation to each other, in combination, hydraulically operableexpansible chamber mechanism for holding the inlet valve open through aportion of the compression stroke of the piston, a hydraulic impulsegiver having means for varying the period it delivers its impulse, meansconnecting said impulse giver with said hydraulically operableexpansible chamber mechanism whereby impulses delivered by the formercontrol the operation of the latter, and means governed by compressordischarge pressure for adjusting said means for varying the periodduring which the expansible chamber mechanism is subject to the impulse.

17. In an apparatus for varying the quantity of fluid delivered perstroke by. a compressor which includes a reciprocable piston, a cylinderfor said piston, said cylinder and pistoncoacting to form a chamber inwhich compression of a fluid is eflected by relative movement betweensaid cylinder and piston, said cylinder having an inlet valve, a shaftand a connection between said shaft and piston such that they move ingiven relation to each other, in combination, hydraulically operableexpansible chamber mechanism for holding the inlet valve open through aportion of the compression stroke of the piston,

a hydraulic impulse giver havingmeans for varying the instant at whichit delivers its impulse, means connecting said impulse giver with saidhydraulically operable expansible chamber mechanism whereby impulses.delivered by the former control the operation of the latter, and meansgoverned by compressor discharge pressure for adjusting said means forvarying the instant of delivery of the impulse by said impulse giver tovary such instant. 18. In an apparatus for varying the quantity of fluiddelivered per stroke bya compressor which includes a reciprocablepiston, a cylinder for said piston, said cylinder and piston coacting toform a chamber in which compression of a fluid is effected by relativemovement between said cylinder and piston, said cylinder having an inletvalve, a shaft and a connection between said shaft and piston such thatthey move in given relation to each other, in combination, hydraulicallyoperable expansible chamber mechanism for holding the inlet valve openthrough a portion of the compression stroke of the piston, a hydraulicimpulse giver having means for varying the period during which fluiddelivered by the impulse giver is displaced, means connecting saidimpulse giver with said hydraulically operable expansible chambermechanism whereby impulses-delivered by the former control the operationof the latter, and means governed by compressor discharge pressure foradjusting said means for varying the period of fluid displacement bysaid impulse giver to vary such period.

19. In an apparatus for varying the quantity of fluid delivered perstroke by a compressor which includes a reciprocable piston, a cylinderfor said piston, said cylinder and piston coacting to form a chamber inwhich compression of a fluid is efiected by relative movement betweensaid cylinder and piston, said cylinder having an inlet valve, a shaftand a connection between said shaft and piston such that they move ingiven relation to each other, in combination, hydraulically operableexpansible chamber mechanism for holding the inlet valve open through aportion of the compression stroke of the piston, a hydraulic impulsegiver having means for providing impulses of varied duration but havinglike initiations, means connecting said impulse giver with saidhydraulically operable expansible chamber mechanism whereby impulsesdelivered by the former control the operation of the latter, and meansgoverned by compressor discharge pressure for adjusting said means forvarying the durations of delivery of the impulse by said impulse giverto vary such durations. I

20. In an apparatus for varying the quantityof fluid delivered perstroke by a compressor which includes a reciprocable piston, a cylinderfor said piston, said cylinder and piston coacting to form a chamber inwhich compression of a fluid is effected by relative movement betweensaid cylinder and piston, said cylinder having an inlet valve, a shaftand a connection between said shaft and piston such that they move in agiven relation to each other, in combination, hydraulically operableexpansible chamber mechanism for holding the inlet valve open through aportion of the compression stroke of the piston, a hydraulic impulsegiver, means connecting said impulse giver with said hydraulicallyoperable expansible chamber mechanism whereby impulses delivered by theformer control the operation of the latter, said hydraulic impulse giverhaving a fluid displacing plunger reciprocable to displace fluid to saidhydraulically operable expansible chamber mechanism and rotatable tovary the period during which it provides an impulse, means forinitiating the fluid displacing stroke of said plunger during thesuction stroke of said piston, and means governed by compressordischarge pressure for adjusting the duration of the impulse.

21. In an apparatus of the character described, in combination, afree-piston motor-compressor including at least one pair of motorpistons each having a compressor piston connected with it forreciprocation, means for delivering varied quantities of fuel toefiectactuation of the motor pistons, means for varying the quantity of fluidpumped by the compressor pistons, means governed by the dischargepressure against which the compressor pistons deliver fluid foreflecting an increase in the quantity of fuel delivered proportional tothe increase in work load efiective until the discharge pressure reachesthe lower limit of a desired pressure spread within which themotor-compressor is intended normally to operate, and means efiectivethereafter and until the upper limit of such pressure spread is reachedand also governed by the discharge pressure against which the compressorpistons deliver fluid for progressively cutting down the quantity of airdelivered as pressure increases and for concurrently progressivelyreducing the quantity of fuel injected.

22. In an apparatus for varying the quantity of fluid delivered perstroke by a compressor which includes a reciprocable piston, a cylinderfor said piston, said cylinder and piston coacting to form a chamber inwhich compression of a fluid is eflected by relative movement betweensaid cylinder and piston, a shaft and a connection between said shaftand piston such that they move in given relation to each other, incombination, hydraulically operable means for eflecting venting of saidcylinder during a portion of the compression stroke of the piston, ahydraulic impulse giver having means for varying the duration of thetime it delivers its impulse, means connecting said impulse giver withsaid hydraulically operable means whereby impulses delivered by theformer control the operation of the latter, and means governed bycompressor discharge pressure for adjusting said means for varying theduration of the time of delivery of the impulse by said impulse giver tovary such duration.

23. In an apparatus for varying the quantity of fluid delivered perstroke by a compressor which includes a reciprocable piston, a cylinderfor said piston, said cylinder and piston coacting to form a chamber inwhich compression of a fluid is effected by relative movement betweensaid cylinder and piston, said cylinder having an inlet valve, anoscillating shaft and a connection between said shaft and piston suchthat they move in synchronism, in combination, hydraulically operableexpansible chamber mechanism for holding the inlet valve open through aportion of the compression stroke of the piston, a hydraulic impulsegiver having means for varying the time it delivers its impulse, conduitmeans connecting said impulse giver with said hydraulically operableexpansible chamber mechanism whereby impulses delivered by the formercontrol the operation of the latter, and means governed by compressordischarge pressure for adjusting said means for varying the time ofdelivery of the impulse by said impulse giver to vary such time.

24. In an apparatus for varying the quantity of fluid delivered perstroke by a compressor which includes a reciprocable piston, a cylinderfor said piston, said cylinder and piston coacting to form a chamber inwhich compression of a fluid is efiected by relative movement betweensaid cylinder and piston, said cylinder having an inlet valve, a shaftand a connection between said shaft and piston such that they move insynchronism, in com-' bination, hydraulically operable expansiblechamber mechanism for holding the inlet valve open through a portion ofthe compression stroke of the piston, a hydraulic impulse giver havingmeans for varying the period during which it displaces fluid, meansconnecting said impulse giver with said hydraulically operableexpansible chamber mechanism whereby impulses delivered by the formercontrol the operation of the latter, and means governed by compressordischarge pressure for adjusting said means for varying the period offluid displacement by said impulse giver to vary such period.

25. In combination, in a motor driven compressor which comprisesfuel-pumping means having an adjustment for the quantity of fuel pumpedand which further comprises a device for varying the quantity of fluiddelivered per stroke which device has an adjustment which controls thequantity of delivered fluid, a pressure responsive device responsive tocompressor discharge pressure from a base pressure to the lower limit ofthe designed operating range, another pressure responsive deviceresponsive to compressor discharge pressure from said lower limit tomaximum desired compressor discharge pressure, an operating connectionbetween said first mentioned pressure responsive device and said firstmentioned adjustment by which said pressure responsive device causessaid adjustment to increase fuel supply with increasing compressordischarge pressure, said operating connection including a lever havingthree points therealong at which connections thereto are made, saidfirst mentioned pressure responsive device being connected to one ofsaid connection points and said first mentioned adjustment beingconnected at another of said points, on operating connection betweensaid second mentioned pressure responsive device and said secondmentioned adjustment by which said second mentioned pressure responsivedevice causes said second mentioned adjustment to reduce the quantity offluid compressed and delivered per stroke as compressor dischargepressure increases from said lower limit, and a further connectionactuated by said second mentioned pressure responsive device andconnected with the third of said connection points for causing saidfirst mentioned adjustment to reduce fuel delivery progressively asreduction in fluid delivered takes place.

References Cited in the filo of this patent or the original patentUNITED STATES PATENTS 1,572,998 Harris Feb. 16, 1926 2,064,976 JanickeDec. 22, 1936 2,086,228 Janicke July 6, 1937 2,115,921 Steiner May 3,1938 2,130,721 Kadenacy Sept. 20, 1938 2,132,083 Pescara Oct. 4, 19382,147,935 Steiner Feb. 21, 1939 2,408,399 Kadenacy Oct. 1, 19462,473,204 Huber June 14, 1949 2,501,056 Kalitinsky Mar. 21, 19502,535,558 Welsh Dec. 26, 1950 2,611,233 Welsh Sept. 23, 1952 2,638,266Meitzler May 1.2, 1953 2,666,569 Bent Ian. 19, 1954 FOREIGN PATENTS539,953 Great Britain Sept. 30, 1941

